// promise
let promise = new Promise((resolve, reject) => {
  resolve('hello')
})

promise.then(res => {
  return res + ' lagou'
}).then(res => {
  return res+' I Love You'
},err => {
  console.log(err)
}).then(res => {
  console.log(res)
}, err => {
  console.log(err)
}).catch(err=> {
  console.log('1-',err.Error)
})